Video coding is a way of transforming a series of video images into a compact digitized bit-stream so that the video images can be transmitted or stored. An encoding device is used to code the video images, with an associated decoding device being available to reconstruct the bit-stream for display and viewing. A general aim is to form the bit-stream so as to be of smaller size than the original video information. This advantageously reduces the capacity required of a transfer network, or storage device, to transmit or store the bit-stream code.
Common standardized approaches have been adopted for the format and method of the coding process, especially with respect to the decoding part. For example, a video encoding format being standardized is High Efficiency Video Coding (HEVC), wherein each video image is split into macroblocks called Coding Units (CU) that are partitioned and adjusted according to the characteristics of the original image segment under consideration. This allows more detailed coding of areas of the video image which contain relatively more information and less coding effort for those areas with fewer features.
The video images were originally processed by coding each macroblock individually, in a manner resembling the digital coding of still images or pictures. Later coding models allow for prediction of the features in one frame, either from neighboring macroblocks (spatial prediction), or by association with a similar macroblock in a neighboring frame (temporal prediction). This allows use of already available coded information, thereby shortening the amount of coding bit-rate needed overall. Differences between the source area and the area used for prediction are captured in a residual set of values which themselves are encoded in association with the code for the source area. Many different types of predictions are possible. Effective coding chooses the best model to provide image quality upon decoding, while taking account of the bit-stream size each model requires to represent an image in the bit-stream. A trade-off between the decoded picture quality and reduction in required bitrate, also known as compression of the data, is the overall goal.
There exists a continuous need to increase the value of this trade-off for increasing the visual quality of the decoded images while decreasing the required bandwidth to transmit the encoded images.